The Open Systems Interconnection (OSI) model was developed by the International Standards Organization (ISO) in 1983 to provide a conceptual model on which networks could be based. Layer-3 of the OSI model, the network layer, defines how traffic gets across networks. More particularly, layer-3 defines an addressing scheme that includes both network and host addresses, mechanisms for traffic control, and often, a checksum. The most well-known examples of layer-3 protocols are NetBEUI, Internet Protocol (IP), Internet Control Message Protocol (ICMP), Internet Packet Exchange (IPX), and Asynchronous Transfer Mode (ATM).
The network layer allows any two systems to address each other, regardless of whether or not they are directly connected. In order to accomplish this, the network layer includes routing protocols, such as IS-IS, RIP, and OSPF. It also includes packet fragmentation and reassembly, which allows packets to traverse networks with different maximum packet sizes or Maximum Transfer Units (MTUs).
Network components that connect different networks and switch packets are called routers. The OSI model refers to them as Intermediate Systems (ISs), hence the routing protocol IS-IS. Routers by definition exist at the network layer. However, as network technology evolves, the distinct capabilities of bridges, routers, and switches merge into single devices. Accordingly, the term “router” is also contemplated to encompass routers that include these additional technologies.
For more information on networking and routers, the reader is referred to Northrup, A., NT Network Plumbing, Routers, Proxies, and Web Services, IDG Books World Wide, Inc. 1998 and Isemiger. D., Inside Windows NT Infrastructures, Wiley Computer Publishing, 1998
To maintain the network layer in operation, administration is required. Typically, a network administrator performs on-going measurements of network utilization, router status, loads on servers, overall network performance and the like. To assist in this purpose, Microsoft's “WINDOWS NT” brand operating system includes a utility for configuring a network to include a directory service (DS). The DS maintains a list of routers and RAS servers within the network layer. By accessing the DS, the network administrator can view a listing of all routers and RAS servers within the network.
While the DS in its current implementation works for its intended purpose of maintaining a list of routers and RAS servers on the network, it is deficient in that it fails to provide any further information to a network administrator regarding the attributes of the routers or RAS servers. Furthermore, the DS fails to provide a means by which the network administrator can sort through the list of routers and RAS servers. Accordingly, a need exists for an administration tool that allows a network administrator to selectively access useful information concerning the components residing in the network layer.